Why Are Moths and Other Insects Attracted to Light?
The technical term for this phenomenon is phototaxis, meaning the movement toward or away from light, artificial or otherwise. As for the various theories, they are manifold: 1) moths’ varying sensitivities to UV and white light—apparently, more so than yellow or red light; 2) they become disoriented in their celestial navigation (aka transverse orientation) and can’t keep a constant angular orientation to the moon in order to fly in a straight line; 3) Henry Hsiao’s untested “Mach Band” theory related to optical illusions; 4) possible dielectric disturbances between the male moth’s two antennae at 55 Hz (where “the [bees-wax, altar] candle flame [serves] as a sexual mimic of the coded [far] infrared wavelengths from a [female] moth sex scent pheromone”); and 5) the lack of evolutionary response due to the short time since the introduction of artificial light pollution sources.
In summary, artificial light of various wavelengths seems to cause behavioral disorientation (aka flight-to-light) and “disrupts interspecific interactions,” according to Longcore and Rich (2002). However, the evidence for any of these theories (excepting perhaps number four above) is weak and needs further investigation (Frank, 1988).
Philip S. Callahan, “Moth and Candle: the Candle Flame as a Sexual Mimic of the Coded Infrared Wavelengths from a Moth Sex Scent (Pheromone),” Applied Optics 16 (December 1977): 3089-3097.
Kenneth D. Frank, “Impact of Outdoor Lighting on Moths: An Assessment,”
Journal of the Lepidopterists’ Society 42 (no. 2, 1988): 63-93.
Travis Longcore and Catherine Rich, “Ecological Light Pollution,” Frontiers in Ecology and the Environment 2 (no. 4, 2002): 191-198.